Boeing X-43

The X-43 is an unmanned experimental hypersonic aircraft design with multiple planned scale variations meant to test different aspects of highly supersonic flight. It is part of NASA's Hyper-X program.
The initial version, the X-43A, was designed to operate at speeds greater than Mach 7, about 8,050 km/h (5,000 mph) at altitudes of 100,000 feet (30,000 m) or more. The X-43A is a single-use vehicle and is designed to crash into the ocean without recovery. Three of them have been built: the first was destroyed; the other two have successfully flown, with the scramjet operating for approximately 10 seconds, followed by a 10 minute glide and intended crash.
The second X43-A flew in at about Mach 7 on March 27, 2004. This test made the X-43A the fastest free flying air-breathing aircraft in the world.

The third flight of a Boeing X-43A set a new speed record of 7,000 mph (11,200 km/h), or Mach 9.8, on November 16, 2004. It was boosted by a modified Pegasus rocket which was launched from a Boeing B-52 at 13,157 meters (43,166 feet). After a free flight where the scramjet operated for about ten seconds, the craft made a planned crash into the Pacific ocean off the coast of southern California.
The X-43A aircraft was a small unpiloted test vehicle measuring just over 12 feet (3.7 m) in length. The vehicle was a lifting body and waverider design, where the body of the aircraft provides a significant amount of lift for flight, rather than relying on wings. The aircraft weighed roughly 3,000 pounds or about 1,300 kilograms. The X-43A was designed to be fully controllable in high-speed flight, even when gliding without propulsion. However, the aircraft was not designed to land and be recovered. Test vehicles crashed into the Pacific Ocean when the test was over.

The craft was created to develop and test an exotic type of engine called a supersonic-combustion ramjet, or "scramjet," an engine variation where external combustion takes place within air that is flowing at supersonic speeds. The X-43A's developers designed the aircraft's airframe to positively affect propulsion, just as it affects aerodynamics: in this design, the forebody is a part of the intake airflow, while the aft section functions as a nozzle.

Scramjets only operate at hypersonic speeds in the range of Mach 6 or higher, so rockets or other jet engines are required to initially boost scramjet-powered aircraft to this base velocity. In the case of the X-43A, the aircraft was accelerated to high speed with a Pegasus rocket launched from a converted B-52 Stratofortress bomber.